Yahyarelated to me from Malik from Ibn Shihab that Said al-Musayyab and AbuBakr ibn Abd ar-Rahman said about a man who made a vow to abstain fromintercourse with his wife, "If four months pass it is a divorce. Thehusband can go back to his wife as long as she is in her idda."
USC-MSA web (English) reference: Book 29, Hadith 18
Arabic reference: Book 29, Hadith 1172